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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 6 |
| 5 | 10 |
| 6 | 21 |
| 7 | 28 |
| 8 | 36 |
| 9 | 45 |
| 10 | 55 |
| 11 | 66 |
| 12 | 78 |
| 13 | 171 |
| 14 | 465 |
| 15 | 528 |
| 16 | 666 |
| 17 | 2211 |
| 18 | 4465 |
| 19 | 22791 |
| 20 | 333336 |
[0,1,3,6,10,21,28,36,45,55,66,78,171,465,528,666, 2211,4465,22791,333336] |